Drain, waste, and vent fittings (referred to as “DWV fittings” or “DWV pattern fittings”) have been used for many years to move liquids at low pressures using gravity. DWV fittings are used to move waste liquids and solids out of bathrooms and kitchens and into sanitary sewers. DWV pattern fittings are also used to plumb, as drains for roof and floor, in industrial processes, in institutional settings, and in commercial waste systems.
DWV fittings for handling non-corrosive waste have been constructed of many materials: clay, iron, copper, ABS plastic, and PVC plastic. DWV fittings are generally of the type having sweeping full bore solids handling design and fall. “Fall” as that term is used in drain systems means to move the material and keep the pipe from filling with solids. Typical fall is about ¼″ per foot, meaning every foot of pipe is ¼″ lower than the last. This fall is typically built into the fittings. For example, in the case of a sanitary tee branch, the sanitary tee branch isn't exactly 90 degrees, so that when pipe is attached to it, the tee branch approaches at a slope of about ¼″ per foot.
Problems, however, arise when DWV fittings are used in piping systems that handle corrosive waste. As used herein, “corrosive waste” includes waste such as chemical corrosives and/or waste that can reach temperatures of about 210 degrees Fahrenheit. One problem with present DWV fittings used for corrosive wastes is that present fittings are susceptible to the formation of leaks over time. Another problem is that installation of present fittings can be cumbersome and time consuming.
DWV fittings for handling corrosive waste have typically been constructed of either polyolefin ASTM F1412-01, specifically polypropylene (PP) with a flame retardant added, or polyvinylidene Fluoride ASTM F1673-95. These fittings can require a mechanical joint connection system or a fusion connection system to connect pipe to fittings. The mechanical joining method is time consuming and prone to leaking after time because the plastic moves and the joint loosens. The fusion method is difficult, cumbersome, and requires special equipment. Most fusion systems use metal coils and an electrical device to heat and melt the two surfaces to be joined. These metal coils remain in the middle of the joint and can be corroded away causing a leak-path if they become exposed on the inside. The fusion joining method is not consistently dependable. The fusion joining method varies in consistency based on the quality of power available on the job sites, the skill of the installer, and the required dimensional stability of the parts to be joined. Leaks are not uncommon in corrosive waste systems that use polyolefin DWV fittings and polyvinylidene fluoride DWV fittings.
Accordingly, there is a need for DWV fittings that avoid the aforementioned problems of difficulty in installation and susceptibility to leaks in the prior art.